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Thursday, 10 September 2015

Ancient DNA Elucidates Basque Origins

Researchers find that the people of northern Spain and southern France are an amalgam of early Iberian farmers and local hunters.

Is the fog lifting on mysterious Basque 


The mysterious origins of the Basque people of northern Spain and southern France have become a little clearer thanks to DNA extracted from centuries-old human remains unearthed in a Spanish cave. Nearly 700,000 Basques, who speak a globally unique language and retain genetic patterns that distinguish them from other Europeans, seem to be descendants of Neolithic farmers who mixed with local hunters before becoming genetically isolated from the rest of Europe for millennia.

Researchers led by population geneticist Mattias Jakobsson from Uppsala University in Sweden analyzed DNA from eight skeletons pulled out of El Portalón cave in the Basque country of northern Spain. The team compared the genomes extracted from the remains, dated to between 3,500 and 5,500 years old, to modern European genomes and more than 12 ancient genomes from 5,000- to 8,000-year-old skeletons from Western and Central Europe. The El Portalón skeletons retained genetic traces that tied them more closely to modern-day Basques than any other European. Jakobsson and his coauthors reported their results yesterday (September 8) in PNAS.

The researchers suggested that early Basques likely sheltered from waves of European migration that began about 5,000 years ago. “It’s hard to speculate, but we’ve been working with Basque historians and it’s clear from the historical record that this area was very difficult to conquer,” Jakobsson told BBC News.

The findings contradict earlier models, which suggested Basque people were genetically distinct from other Europeans because they represented a relic population of ancient hunter-gatherers. If that were true, modern Basques would have genetic signatures that were more similar to ancient DNA recovered from hunter-gatherers rather than to the El Portalón remains. “We can finally set aside this old story,” Jakobsson told Science.

Ancient genomes link early farmers to Basques

September 7, 2015
Uppsala University
A surprising discovery from the genomes of eight Iberian Stone-Age farmer remains has been reported. The analyses revealed that early Iberian farmers are the closest ancestors to modern-day Basques, in contrast previous hypotheses that linked Basques to earlier pre-farming groups.

The burial was found deliberately sheltered by large limestone blocks and three other blocks carefully protected the child´s head. The grave was scattered with grave goods suggesting a special status of this boy. The burial is covered by different ornaments, such as ceramics fragments of different sizes sealed with a green-like clay, vessel parts, flint flakes, a bone arrowhead, quartzite and, most surprisingly, the boy was left accompanied by an almost complete calf in anatomical position. This child possibly died of malnutrition as evidenced by a series of lesions in his skull and bones indicating the boy suffered from rickets and/or scurvy (Castilla et al, 2014) at different stages of his life.
Credit: Eneko Iriarte
An international team led by researchers at Uppsala University reports a surprising discovery from the genomes of eight Iberian Stone-Age farmer remains. The analyses revealed that early Iberian farmers are the closest ancestors to modern-day Basques, in contrast previous hypotheses that linked Basques to earlier pre-farming groups.

The team could also demonstrate that farming was brought to Iberia by the same/similar groups that migrated to northern and central Europe and that the incoming farmers admixed with local, Iberian hunter-gather groups, a process that continued for at least 2 millennia.

The study is published ahead of print in the scientific journal Proceedings of the National Academy of Sciences, PNAS.

Most of the previous studies about the transition from small and mobile hunter-gatherer groups to larger and sedentary farming populations have focused on central and northern Europe, however much less in known about how this major event unfolded in Iberia. This time, the research team investigated eight individuals associated with archaeological remains from farming cultures in the El Portalón cave from the well-known Anthropological site Atapuerca in northern Spain.

"The El Portalon cave is a fantastic site with amazing preservation of artefact material," says Dr. Cristina Valdiosera of Uppsala University and La Trobe University, one of the lead authors.
"Every year we find human and animal bones and artifacts, including stone tools, ceramics, bone artefacts and metal objects, it is like a detailed book of the last 10,000 years, providing a wonderful understanding of this period. The preservation of organic remains is great and this has enabled us to study the genetic material complementing the archaeology," Dr. Cristina Valdiosera continues.

From these individuals who lived 3,500-5,500 years ago, the authors generated the first genome-wide sequence data from Iberian ancient farmers and observed that these share a similar story to those of central and northern Europe. That is, they originate from a southern wave of expansion, and also admixed with local hunter-gatherer populations and spread agricultural practices through population expansions. The authors noticed that although they share these similarities with other European farmers, this early Iberian population has its own particularities.

"We show that the hunter-gatherer genetic component increases with time during several millennia, which means that later farmers were genetically more similar to hunter-gatherers than their forefathers who brought farming to Europe," says Dr. Torsten Günther of Uppsala University and one of the lead authors.

"We also see that different farmers mixed with different hunter-gatherer groups across Europe, for example, Iberian farmers mixed with Iberian hunter-gatherers and Scandinavian farmers mixed with Scandinavian hunter-gatherers." Dr. Cristina Valdiosera adds.

The study also reports that compared to all modern Spanish populations, the El Portalón individuals are genetically most similar to modern-day Basques. Basques have so far -- based on their distinct culture, non-indo-European language, but also genetic make-up -- been thought of as a population with a long continuity in the area, probably since more than 10,000 years ago.

"Our results show that the Basques trace their ancestry to early farming groups from Iberia, which contradicts previous views of them being a remnant population that trace their ancestry to Mesolithic hunter-gatherer groups," says Prof. Mattias Jakobsson of Uppsala University, who headed the study.
"The difference between Basques and other Iberian groups is these latter ones show distinct features of admixture from the east and from north Africa." he continues.

These findings shed light into the demographic processes taking place in Europe and Iberia during the last 5,000 years which highlights the unique opportunities gained from the collaborative work of archaeologists, anthropologists and geneticists in the analysis of ancient DNA.

"One of the great things about working with ancient DNA is that the data obtained is like opening a time capsule. Seeing the similarities between modern Basques and these early farmers directly tells us that Basques remained relatively isolated for the last 5,000 years but not much longer," says Dr. Torsten Günther.

Story Source:
The above post is reprinted from materials provided by Uppsala University. Note: Materials may be edited for content and length.

Journal Reference:
  1. Günther et al. Ancient genomes link early farmers from Atapuerca in Spain to modern-day Basques. PNAS, September 2015 DOI: 10.1073/pnas.1509851112

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